Light Emitting Diodes (LEDs) have many advantages over conventional light sources, such as incandescent, halogen and fluorescent lamps. These advantages include longer operating life, lower power consumption, and smaller size. Consequently, conventional light sources are increasingly being replaced with LEDs in traditional lighting applications. As an example, LEDs are currently being used in flashlights, camera flashes, traffic signal lights, automotive taillights and display devices.
Among the various packages for LEDs, an LED package of interest is the Plastic Leaded Chip Carrier (PLCC) package for a surface mount LED. Surface mount LEDs in PLCC packages may be used, for example, in automotive interior display devices, electronic signs and signals, and electrical equipment.
In some LED applications, a narrow viewing angle LED is required. As used herein, a narrow viewing angle refers to limiting the viewing angle (also referred to as the spatial radiation pattern) of less than or equal to 80 degrees (i.e., less than or equal to 40 degrees off-axis). When the LED is packaged within traditional PLCC and the LED naturally emits light at a relatively wide viewing angle, the PLCC package must be modified to accommodate a narrow viewing angle.
As can be seen in FIG. 1, traditional PLCC packages 100 for LEDs include cast epoxy/silicone on a plastic molded lead frame 104 which includes a plastic molded cup 108 and one or more leads which constitute a lead frame 112. Traditional plastic molded lead frames 104 are provided with a reflector cup into which the LED is mounted. The reflector cup in traditional plastic molded lead frames 104 is generally uniform in nature in that the inner wall of the reflector cup has a single offset or tilt angle relative to the surface on which the LED is mounted. If a white LED is desired, then epoxy/silicone can be provided in the reflector cup with phosphor. In previous solutions, a narrow viewing angle was achieved for PLCC packages 100 by attaching a lens 116 to the plastic molded cup 108. The profile of the lens 116 is specifically formed to minimize the viewing angle of the LED in the PLCC package.
There are several downsides to utilizing a lens 116 to achieve a narrow viewing angle. First, the addition of more components to the PLCC package increases its cost. Second, the lens 116 is usually attached with glue, which is also a complicated process and is not necessarily that easy to control. Third, the viewing angle for the LED will not be accurate if the lens 116 is tilted in any way or offset relative to the LED during the assembly process.